The present invention relates to an apparatus for locating sources of sound in water. More particularly, the present invention relates to such an apparatus which includes a hydrophone system whose one given reference axis is automatically aligned with the earth's magnetic field by mechanically coupling the hydrophone system with a compass magnet (north reference) and with the hydrophone system being set out in the water while suspended under a buoy at a distance therefrom.
It is known to build a hydrophone system into a floating buoy element and to drop such an arrangement from an aircraft. As soon as the buoy lands on the water, the hydrophone system is released and exits from the buoy body and is submerged to a given depth. Received sound signals in the water are then transmitted by the hydrophone system via a cable to a transmitter fastened to the buoy body where the water sound signals are converted and emitted. These emitted signals are received by the aircraft and are evaluated according to known evaluation processes.
German Offenlegungsschrift (Laid-Open Patent Application) No. 1,516,645, published on June 26, 1969 ( which corresponds to a combination of U.S. Pat. Nos. 3,286,224 and 3,319,218 issued Nov. 15, 1966 and May 9, 1967, respectively) discloses an arrangement in which the hydrophone system is rotated to have its reference axis in the north-south direction of the magnetic field of the earth in order to obtain the direction of the impinging water sound signals with reference to north. Such a device, however, can furnish only inaccurate ranging information since the connecting wires which are disposed between the hydrophones and the buoy body for holding the hydrophones and for transmitting the ranging information prevent accurate alignment of the hydrophone with the north direction.